Immediate Copy Target Pull of Volume Data

ABSTRACT

A composite storage server employs a plurality of distributed storage sites including a mount site, a source copy site and one or more copy target sites for executing a storage of volume data within the composite storage server. In operation, an immediate copy target site receives a communication of a source copy complete message from the mount site, the source copy complete message being indicative of the source copy site having a complete copy of the volume data. Based on the source copy complete message, the immediate copy target site pulls the volume data from a peer distributed storage site having a complete copy of the volume data (e.g., the source copy site, the mount site or another copy target site).

FIELD OF THE INVENTION

The present invention generally relates to the storage of volume datawithin a composite storage server. The present invention specificallyrelates to the storage of volume data within immediate copy target sitesof the composite storage server.

BACKGROUND OF THE INVENTION

A composite storage server consists of multiple distributed storagesites for a selective storage of volume data within two or more of thedistributed storage sites. Typically, each distributed storage siteemploys a job director and for any given storage job, one of thedistributed storage sites serves as a single source copy site wherebyits director, upon completion of the volume data being pushed to itscache, will pull the cached volume data from its cache to thereby pushthe cached volume data to any of the other distributed storage sitesdesignated as copy target sites for purposes of the storage job.

Clearly, the single source copy site demands significant processingpower to being able to pull and push the cached volume data to the copytarget sites, particularly in view of a substantial number of copytarget sites and any concurrent execution of other storage jobs withinthe composite storage server. Furthermore, each copy target site has aservant role in terms of being excluded from the decision process by thesource copy site of when, where and how fast the volume data is pushedto each copy target site and therefore also demands significantprocessing power, particularly in view of any concurrent execution ofother storage jobs within the composite storage server whereby a copytarget site may or may not serve as a source copy site for one or moreof those storage jobs. Therefore, it would be invaluable for a compositestorage server to incorporate a technique for distributing theresponsibility of storing volume data within the composite storageserver among the distributed storage sites whereby each distributedstorage site involved in the storage of the volume data within thecomposite storage server is an active participant.

SUMMARY OF THE INVENTION

The present invention provides a new and unique immediate copy targetpull of volume data.

A first form of the present invention is a composite storage servercomprising a plurality of distributed storage sites including a mountsite, a source copy site and at least one copy target site for executinga storage of volume data within the composite storage server. Inoperation, the immediate copy target site receives a communication of asource copy complete message from the mount site, the source copycomplete message being indicative of the source copy site having acomplete copy of the volume data. Based on the source copy completemessage, the immediate copy target site pulls the volume data from apeer distributed storage site having a complete copy of the volume data(e.g., the source copy site, the mount site or another copy targetsite).

In a composite storage server comprising a plurality of distributedstorage sites including a mount site, a source copy site and at leastone copy target site for executing a storage of volume data within thecomposite storage server, the second form of the present invention is animmediate copy target site comprising a processor, a memory storinginstructions operable with the processor. The instructions are executedfor receiving a communication of a source copy complete message from themount site, the source copy complete message being indicative of thesource copy site having a complete copy of the volume data, and based onthe source copy complete message, for pulling the volume data from apeer distributed storage site having a complete copy of the volume data(e.g., the source copy site, the mount site or another copy targetsite).

In a composite storage server comprising a plurality of distributedstorage sites including a mount site, a source copy site and at leastone copy target site for executing a storage of volume data within thecomposite storage server, the third form of the present invention is amethod of operating the immediate copy target site. The method involvesthe immediate copy target site receiving a communication of a sourcecopy complete message from the mount site, the source copy completemessage being indicative of the source copy site having a complete copyof the volume data. Based on the source copy complete message, themethod further involves the immediate copy target site pulling thevolume data from a peer distributed storage site having a complete copyof the volume data (e.g., the source copy site, the mount site oranother copy target site).

The aforementioned forms and additional forms as well as objects andadvantages of the present invention will become further apparent fromthe following detailed description of the various embodiments of thepresent invention read in conjunction with the accompanying drawings.The detailed description and drawings are merely illustrative of thepresent invention rather than limiting, the scope of the presentinvention being defined by the appended claims and equivalents thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary embodiment of a composite storage serverin accordance with the present invention;

FIG. 2 illustrates a flowchart representative of a general embodiment ofa volume data storage method in accordance with the present invention;

FIG. 3 illustrates an exemplary configuration of the composite storageserver illustrated in FIG. 1 prior to an execution of a storage job inaccordance with the present invention;

FIG. 4 illustrates one embodiment of a host job manager in accordancewith the present invention;

FIG. 5 illustrates a flowchart representative of one embodiment of amount side pre-source copy management method in accordance with thepresent invention;

FIG. 6 illustrates an exemplary operational state of the compositestorage server illustrated in FIG. 3 based on a host message activationin accordance with the present invention;

FIG. 7 illustrates a flowchart representative of one embodiment of ahost job message activation method in accordance with the presentinvention;

FIG. 8 illustrates a flowchart representative of one embodiment of asource copy management method in accordance with the present invention;

FIG. 9 illustrates an exemplary operational state of the compositestorage server illustrated in FIG. 3 based on a host volume data push inaccordance with the present invention;

FIG. 10 illustrates a flowchart representative of one embodiment of amount side post-source copy management method in accordance with thepresent invention;

FIG. 11 illustrates a flowchart representative of one embodiment of animmediate copy management method in accordance with the presentinvention;

FIG. 12 illustrates an exemplary operational state of the compositestorage server illustrated in FIG. 3 based on an immediate copy targetvolume data pull in accordance with the present invention;

FIG. 13 illustrates a flowchart representative of one embodiment of adeferred copy management method in accordance with the presentinvention; and

FIG. 14 illustrates an exemplary operational state of the compositestorage server illustrated in FIG. 3 based on a deferred copy targetvolume data pull in accordance with the present invention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

FIG. 1 illustrates a composite storage server 10 for storing volume dataon behalf of hosts 70-73. To this end, composite storage server 10employs a distributed storage site 20 connected to host 70, adistributed storage site 30 connected to host 71, a distributed storagesite 40 connected to host 72 and a distributed storage site 50 connectedto host 73. Distributed storage site 20-50 are interconnected as peersites by a network 60 via a control path and a data path.

Distributed storage site 20 includes a processor 21 and a memory 22supporting a host job manager 23, a data mover 24 and a cache 25.Distributed storage site 30 includes a processor 31 and a memory 32supporting a host job manager 33, a data mover 34 and a cache 35.Distributed storage site 40 includes a processor 41 and a memory 42supporting a host job manager 43, a data mover 44 and a cache 45.Distributed storage site 50 includes a processor 51 and a memory 52supporting a host job manager 53, a data mover 54 and a cache 55.

Each host 70-73 from time to time will request an execution of a hostjob directed to storing or modifying volume data within compositestorage server 10 as known in the art. Each host job manager 23-53 is asoftware/firmware module consisting of instructions stored within itsassociated memory 22-52 and executable by its associated processor 21-51for actively participating in the control of a composite storage of avolume data within composite storage server 10 in accordance with theinventive principles of the present invention as will be furtherdescribed herein. Each data mover 24-54 is a software/firmware moduleconsisting of instructions stored within its associated memory 22-52 andexecutable by its associated processor 21-51 for moving volume data inand out of its associated cache 25-55 as known in the art.

Each execution of a host job by composite storage server 10 involves oneof the distributed storage sites 20-50 serving as a mount site, one ormore of the distributed storage sites 20-50 serving as a source copysite, and one or more of the distributed storage sites 20-50 serving asa copy target site, immediate or deferred. For purposes of the presentinvention, the term “mount site” is broadly defined herein for a givenhost job as a distributed storage site performing an overall managementof an execution of the host job by composite storage server 10. The term“source copy site” is broadly defined herein for the host job as adistributed storage site designated by the mount site for storing aprimary copy of volume data pushed to its cache by a host. The term“immediate copy target site” is broadly defined herein for the host jobas any distributed storage site designated by the mount site for pullingand storing a secondary copy of volume data from the source copy site oranother copy target site prior to a complete execution of the host job.And, the term “a deferred copy target site” is broadly defined hereinfor the host job as any distributed storage site designated by the mountsite for pulling and storing a secondary copy of volume data from thesource copy site or another copy target site subsequent to a completeexecution of the host job.

Host job managers 23-53 of respective distributed storage sites 20-50are structurally configured for distributing the responsibility ofstoring volume data within composite storage server 10 as embodied in avolume data storage method of the present invention represented by aflowchart 80 illustrated in FIG. 2. To facilitate an understanding offlowchart 80, FIG. 3 illustrates an example of a host job configurationof composite storage server 10. In this illustrated example, distributedstorage site 20 serves as mount site for administering an overallmanagement of an execution of the host job by composite storage server10 as requested by host 70. Distributed storage site 30 serves as asource copy site designated by mount site 20 for storing a primary copyof volume data pushed to its cache 35 by host 70. Distributed storagesite 40 serves as an immediate copy target site designated by mount site20 for pulling and storing a secondary copy of volume data from sourcecopy site 30 prior to a complete execution of the host job. And,distributed storage site 50 serves a deferred copy target sitedesignated by mount site 20 for pulling and storing a secondary copy ofvolume data from source copy site 30 or immediate copy target site 40subsequent to a complete execution of the host job.

Referring to FIG. 2, a stage S82 of flowchart 80 is predicated on amandatory requirement for a source copy of the volume data and therebyencompasses a mount site of the host job managing a volume data pushfrom its associated host to a source copy site. For example, referringto FIG. 3, host job manager 23 (FIG. 1) of mount site 20 utilizes thecontrol path to prepare source copy site 30 for a volume data push fromhost 70 to cache 35 of source copy site 30 whereby host 70 uses mountsite 20 as a conduit to push the volume data to cache 35 via the datapath.

Referring again to FIG. 2, a stage S84 of flowchart 80 is predicated onan optional requirement for one or more immediate copies of the volumedata during an active state of the host job, and thereby encompasses amount site prompting each designated immediate copy target site toindividually manage a volume data pull from the source copy site oranother copy target site having a complete volume data copy. Forexample, referring to FIG. 3, host job manager 33 (FIG. 1) of sourcecopy site 30 manages cache 35 to provide an availability of the volumedata copy, and host job manager 23 of mount site 20 utilizes the controlpath to prompt host job manager 43 (FIG. 1) of immediate copy targetsite 40 to manage a volume data pull by immediate copy site 40 of a copyof the volume data from cache 35 of source copy site 30 to cache 45.

Referring again to FIG. 3, a stage S86 of flowchart 80 is predicated onan optional requirement for one or more deferred copies of the volumedata during an inactive state of the host job and thereby encompasses amount site prompting each designated deferred copy target site toindividually manage a volume data pull from the source copy site oranother copy target site having a complete volume data copy. Forexample, referring to FIG. 3, host job manager 33 of source copy site 30and host job manager 43 of immediate copy target site 40 managerespective cache 35 and cache 45 to provide an availability of thevolume data copy, and host job manager 23 of mount site 20 utilizes thecontrol path to prompt host job manager 53 (FIG. 1) of deferred copytarget site 50 to manage a volume data pull by deferred copy site 50 ofa copy of the volume data from cache 35 of source copy site 30 to cache55 or from cache 45 of immediate copy site 40 to cache 55.

In practice, a host job manger of the present invention can be embodiedin a variety of structural forms for implementing flowchart 80 that aredependent upon a designed topology of the composite storage server andthe individual structural configurations of each distributed storagesite as would be appreciated by those having ordinary skill in the art.Thus, the following description of an exemplary embodiment 90 of a hostjob manager of the present invention as shown in FIG. 4 is provided tofacilitate a further understanding of the inventive principles of thepresent invention without limiting or restricting in practice thestructural forms of a host job manager of the present invention.

Referring to FIG. 4, host job manager 90 employs a composite storagetable manager 91 and a broadcast message manager 92. Composite storagetable manager 91 is structurally configured to manage a compositestorage table for recording and updating meta-data corresponding to ahost job whereby each distributed storage site can effectively andcooperatively fulfill its responsibility in managing a storage of volumedata within the composite storage server. Broadcast message manager 92is structurally configured to manage a broadcast of messages generatedby host job manager 90 and to interpret messages received by host jobmanager 90 in dependence of an associated distributed storage site'sresponsibility in managing a storage of volume data within the compositestorage server. Collectively, composite storage table manager 91 andbroadcast message manager 92 implement various management methods of thepresent invention for an execution of a host job, such as, for example,the various management methods of the present invention represented bythe flowcharts illustrated in FIGS. 5, 7, 8, 10, 11 and 13.

Specifically, FIG. 5 illustrates a flowchart 100 representative of amount site pre-source copy management method of the present inventionthat is implemented by a distributed host site serving as a mount sitefor a particular host job. A stage S102 of flowchart 100 encompasses thehost job manager of the mount site receiving and acknowledging a hostjob communication from an associated host as known in the art. A stageS104 of flowchart 100 encompasses the host storage manager of the mountsite recording the host job in its composite storage table. In oneembodiment, stage S104 involves the host job manager of the mount siteidentifying one or more source copy sites, any immediate copy targetsites and any deferred copy target sites for executing the host job. Inpractice, the identification of these sites is in view of obtaining anoptimal storage of the volume data within the composite storage server,which is dependent upon a designed topology of the composite storageserver and the individual structural configurations of each distributedstorage site as would be appreciated by those having ordinary skill inthe art.

In this embodiment, stage S104 further involves a generation and arecording of host job meta-data indicative of the identified sites,duplication rules for the volume data, and an active processing statusof the host job. For example, FIG. 6 illustrates mount site 20generating and recording a host job meta-data record 27 within acomposite storage table 26 with the host job meta-data being indicativeof distributed storage site 30 serving as the source copy site,distributed storage site 40 serving as an immediate copy target site,and distributed storage site 50 serving as a deferred copy target site.The host job meta-data further indicates duplication rules and an activestatus of the host job requested by host 70.

Referring again to FIG. 5, a stage S106 of flowchart 100 encompasses thehost job manager of the mount site broadcasting a host job messageincluding the host job meta-data to inform the other sites of theirroles in the storage of the volume data within the composite storageserver and any other necessary information for storing the volume datawithin the composite storage server. For example, as shown in FIG. 6,the host job manager of mount site 20 broadcasts a host job message HJMincluding host job meta-data HJMD to sites 30-50.

In response to the host job message broadcast, each distributed storagesite (including the mount site) implements a host job message activationmethod of the present invention as represented by a flowchart 110illustrated in FIG. 7. Referring to FIG. 7, a stage S112 of flowchart110 encompasses the host job manager of the distributed storage site(s)receiving the host job message broadcast whereby each host job managerrecords the host job message in its composite storage table to therebyread the host job message meta-data during a stage S114 of flowchart 110to determine the subject volume data whereby the host job manager mayterminate any pending host job related to the subject volume data.

Thereafter, the host job manager of the distributed storage site(s)proceed to a stage S116 of flowchart 110 to transition to an idle statefor the subject volume data. At this stage, each host job manager of adistributed storage site serving in as a source copy site in thestorage/modification of the subject volume data in the composite storageserver will be activated by the host to implement a flowchart 120representative of a source copy management method of the presentinvention as will be subsequently explained in connection with FIG. 8.Each host job manager of a distributed storage site serving in as animmediate copy target site in the storage/modification of the subjectvolume data in the composite storage server will be activated by themount site to implement a flowchart 150 representative of a immediatecopy management method of the present invention as will be subsequentlyexplained in connection with FIG. 11. And, each host job manager of adistributed storage site serving in as a deferred copy target site inthe storage/modification of the subject volume data in the compositestorage server will be activated by the mount site to implement aflowchart 160 representative of a deferred copy management method of thepresent invention as will be subsequently explained in connection withFIG. 13.

For example, as shown in FIG. 6, the host job manager of distributedstorage site 20 would determine that mount site 20 does not have a copyrole in the storage of the volume data within composite storage server10 and therefore would terminate flowchart 110 yet save the host jobmeta-data to thereby track any changes to the host job meta-data relatedto the execution of the host job by the other sites. The host jobmanager of distributed storage site 30 would determine that site 30 isserving as the source copy site in the storage of the volume data withincomposite storage server 10, record a host job meta-data record 37 in acomposite storage table 36 and transition to an idle state for thesubject volume data to thereby passively await an activation by host 70to implement flowchart 120 (FIG. 8). The host job manager of distributedstorage site 40 would determine that site 40 is serving as an immediatecopy target site in the storage of the volume data within compositestorage server 10, record a host job meta-data record 47 in a compositestorage table 46 and transition to an idle state for the subject volumedata to thereby passively await an activation by mount site 20 toimplement flowchart 150 (FIG. 11). And, the host job manager ofdistributed storage site 50 would determine that site 50 is serving as adeferred copy target site in the storage of the volume data withincomposite storage server 10, record a host job meta-data record 57 in acomposite storage table 56 and transition to an idle state for thesubject volume data thereby passively await an activation by mount site20 to implement flowchart 160 (FIG. 13).

Referring to FIGS. 5 and 8, subsequent to the host job messagebroadcast, a stage S108 of flowchart 100 encompasses the mount sitemanaging a volume data push from the host to the source copy site. Thisactivates the host job manager of the source copy site to receive thevolume data push from the host via the mount site during a stage S122 offlowchart 120. The volume data push includes the volume data and otheressential information, and in response thereto, the host job manager ofthe source copy site updates the host job meta-data to reflect thevolume data push. This enables the host job manager of the source copysite to write the volume data to a library media (e.g., tape) during astage S124 of flowchart 120 and to maintain the volume data within itsassociated local cache for a specified time period during a stage S126of flowchart 120 to thereby facilitate a volume data pull from each peersite attempting to pull a complete volume data copy from the source copysite.

For example, as shown in FIG. 9, the host job manager of mount site 20manages mount site 20 in serving as a conduit for a volume data push ofvolume data VD and other essential information from host job 70 to cache35 of source copy site 30 whereby the host job manager of source copysite 30 updates host job meta-data record 37 to reflect the volume datapush. Thereafter, the host job manager of source copy site 30 writesvolume data VD to tape residing at site 30 and maintains volume data VDwithin cache 35 for a specified time period to thereby facilitate anyattempted volume data pulls from immediate copy target site 40 and/ordeferred copy target site 50.

Upon completion of the source copy at the source copy site, the mountsite implements a mount site post-source copy management methodrepresented by a flowchart 130 illustrated in FIG. 10. A stage S132 offlowchart 130 encompasses the host job manager of the mount sitereceiving a source copy completion communication from the host wherebythe host job manager of the mount site proceeds to a stage S134 offlowchart 130 to update the host job meta-data based on thecommunication, to broadcast a source copy complete message on thenetwork for purposes of activating any immediate copy target sites toexecute flowchart 150, and to switch on a timer for purposes ofmonitoring the immediate copy target site(s).

Referring to FIG. 11, a stage S152 of flowchart 150 encompasses the hostjob manager of each immediate copy target site receiving the source copycomplete message broadcast whereby the host job manager of eachimmediate copy target site reads the recorded host job meta-data tofacilitate a determination by the immediate copy target site of whichpeer site to pull the volume data to the immediate copy target site inaccordance with its internal data processing rules. Upon reading thehost job meta-data, the host job manager of the immediate copy targetsite proceeds to a stage S154 of flowchart 150 to query its peer sitesfor a complete copy of the volume data. Upon selecting a peer sitehaving a complete volume data copy, the host job manager of theimmediate copy target site will execute a volume data pull from theselected peer site in accordance with its internal processing rule andthe duplication rules, update the host job meta-data to reflect thevolume data pull and broadcast a copy target complete message on thenetwork. This enables the host job manager of the immediate copy site towrite the volume data to library media (e.g., tape) during a stage S156of flowchart 150 and to maintain the volume data within its associatedlocal cache for a specified time period during a stage S158 of flowchart150 to thereby facilitate a volume data pull from each peer siteattempting to pull a complete volume data copy from the immediate copytarget site.

For example as shown in FIG. 12, the host job manager of mount site 20broadcasts a source copy complete message SCM on the network thatactivates the host job manager of immediate copy target site 40 tobroadcast a volume data copy query VDCQ based on the host job meta-datawhereby the host job manager of immediate copy target site 40 woulddetermine a copy of the volume data is located at source copy site 30and therefore would manage a pull of volume data from cache 35 to cache45 and broadcast a copy target complete message CTCM upon completion ofthe volume data pull. Thereafter, the host job manager of immediate copytarget site 40 writes volume data VD to a library media (e.g., tape)residing at site 40 and may maintain volume data VD within cache 45 fora specified time period to thereby facilitate any attempted volume datapull from deferred copy target site 50.

Referring again to FIG. 10, the host job manager of the mount sitemonitors the activities of each immediate copy target site based on theredundancy timer for purposes of providing a redundancy status to thehost.

During an initial execution of a stage S136 of flowchart 130, the hostjob manager of the mount site determines, immediately upon starting theredundancy timer, whether a total number of immediate copy complete(“ICC”) messages indicative of an adequate redundancy in accordance withthe host job meta-data have been received by the mount site. In oneembodiment, a total number of immediate copy complete messages to bereceived by the host job manager of the mount site in accordance withthe host job meta-data is less than or equal to the total number ofimmediate copy target sites whereby the total number of immediate copycomplete messages may be adjusted to reflect each immediate copy targetsite in a down/degraded state.

If it is determined by the host job manager of the mount site duringstage S136 that actual number of received immediate copy completemessages is less than the total number of immediate copy completemessages to be received by the mount site, then the host job manager ofthe mount site proceeds to execute stages S136-S142 to receive anytimely immediate copy complete message and to update the host jobmeta-data based on each timely received immediate copy complete messageuntil such time either (1) the total number of immediate copy completemessage to be received by the host job manager of the mount site havebeen received or (2) the redundancy timer has expired. In oneembodiment, the host job manager of the mount site executes stagesS136-S142 in a passive manner whereby the host job manager of the mountsite is prompted to react to any timely received immediate copy completemessage, an expiration of the redundancy timer and anymessages/indications that an immediate copy target site is in adown/degraded state.

Upon the total number of immediate copy complete messages being receivedby the mount site or an expiration of the redundancy timer, the host jobmanager of the mount site proceeds to a stage S144 of flowchart 140 toupdate the host job meta-data to indicate an inactive status of the hostjob and a redundancy status of the volume data, and to acknowledge thesource copy communication from the host including a redundancy status.The redundancy status will reflect an adequate redundancy if all of therequired immediate copy complete message were received by the host siteprior to the expiration of the redundancy timer whereby the host jobmanager of the mount site proceeds to terminate flowchart 130.

Alternatively, the redundancy status will reflect an inadequateredundancy if all of the required immediate copy complete message werenot received by the host site prior to the expiration of the timerwhereby the host job manager of the mount site transitions the compositestorage server to an immediate-deferred state during a stage S146 offlowchart 140 to thereby proceed to a stage S148 of flowchart 140 toreceive any untimely immediate copy complete messages. In responsethereto, the host job manager of the mount site updates the host jobmeta-data and reports the redundancy status to host 70 as needed.

For example, referring to FIG. 12, mount site 20 determine one immediatecopy complete message ICCM from immediate copy target site 40 ispreferred to be received by mount site 20 prior to the expiration of theredundancy timer. Assuming immediate copy target site 40 is not in adown/degraded state, if the copy target complete message ICCM fromimmediate copy target site 40 is received by mount site 20 prior to theexpiration of the timer, then mount site 20 will acknowledge the sourcecopy complete communication by host 70 with a redundancy statusindicating an adequate number of secondary copies of the volume data arestored within the composite storage server. Otherwise, if the copytarget complete message ICCM from immediate copy target site 40 is notreceived by mount site 20 prior to the expiration of the timer, thenmount site 20 will acknowledge the source copy complete communication byhost 70 with a redundancy status indicating an inadequate number ofsecondary copies of the volume data are stored within the compositestorage server. As a result, the host job manager of mount site 20 willtransition composite storage server 10 to an immediate-deferred statethat is maintained until such time the immediate copy complete messageICCM is sent by immediate copy target site 40 to mount site 20.

Referring to FIG. 10, the inactive processing status of the host job asset by the mount site upon expiration of the timer during stage S144signifies the conclusion of the active status of the host job. Thisactivates each deferred copy target site to manage a pull of the volumedata from the source copy site or a copy target site having a completecopy of the volume data. Specifically, FIG. 13 illustrates a deferredcopy management method of the present invention represented by aflowchart 160. A stage S162 of flowchart 160 encompasses the host jobmanager of the deferred copy target site receiving the source copycomplete message broadcast from the mount site whereby the host jobmanager reads the recorded host job meta-data to facilitate adetermination by the deferred copy target site of which peer site topull the volume data to the deferred copy target site in accordance withits internal data processing rules. Upon reading the host job meta-data,the host job manager of the deferred copy target site proceeds of stageS164 to query its peer sites for an active/inactive status of the hostjob. The host job manager of the deferred copy target site will receivethe current status of the host job from the mount site whereby the hostmanager of the deferred copy target site will proceed to a stage S1168of flowchart 160 upon detecting an inactive status of the host jobduring a stage S166 of flowchart 160 or at is discretion, repeatedlyquery its peer sites for the active/inactive status until such time thehost job manager of the deferred copy target site detects an inactivestatus of the host job.

During stage S168, the host job manager of the deferred copy target sitequeries its peer sites for a complete copy of the volume data. Uponselecting a peer site having a complete volume data copy, the host jobmanager of the deferred copy target site will execute a volume data pullfrom the selected peer site in accordance with its internal processingrule and the duplication rules, update the host job meta-data to reflectthe volume data pull and broadcast a deferred copy complete message onthe network. This enables the host job manager of the deferred copy siteto write the volume data copy to library media (e.g., tape) during astage S170 of flowchart 160 and to maintain the volume data within itsassociated local cache for a specified time period during a stage S172of flowchart 160 to thereby facilitate a volume data pull from each peersite attempting to pull a complete volume data copy from the deferredcopy target site.

For example as shown in FIG. 14, the host job manager of deferred copytarget site 50 broadcast a host job status quest HJSQ on the network andupon detecting an inactive host job status, broadcast volume data copyquery VDCQ based on the host job meta-data whereby the host job managerof deferred copy target site 50 would determine a complete copy of thevolume data is located at source copy site 30 and immediate copy targetsite 40, and therefore would manage a pull of volume data from cache 35or cache 45 to cache 55 and broadcast a deferred copy complete messageDCCM upon completion of the volume data pull. Thereafter, the host jobmanager of deferred copy target site 50 writes volume data VD to taperesiding at site 50 and maintain volume data VD within cache 55 for aspecified time period to thereby facilitate any attempted volume datapull from a peer site.

Referring to FIGS. 1-14, those having ordinary skill in the art willappreciate how to implement the various inventive principles of thepresent invention for a more or less complex composite storage serverthan composite storage server 10 shown in FIG. 1, and in a more or lesscomplex host environment than hosts 70-73 shown in FIG. 1. Furthermore,those having ordinary skill in the art will appreciate variousadvantages of the present invention including, but not limited to, anactive participation to some degree of each distributed storage site ofa composite storage server involved in a storage of a particular volumedata within the server.

Still referring to FIGS. 1-14, is to be also appreciated by those havingordinary skill in the art that (1) a mount site may also serve as asource copy site or a copy target site during the execution of a hostjob, (2) a storing of volume data within a composite storage serverunder the inventive principles of the present invention is inclusive ofan original storage of the volume data within the composite storageserver, an modification/replacement of the volume data as previouslystored within the composite storage server and/or a modification of adata structure/properties of the volume data as stored within thecomposite storage server, and (3) only one copy target site, immediateor deferred, is required for any given host job to maintain redundancy.

The term “processor” as used herein is broadly defined as one or moreprocessing units of any type for performing all arithmetic and logicaloperations and for decoding and executing all instructions related tofacilitating an implementation by a host job manager of the variousvolume data storage methods of the present invention. Additionally, theterm “memory” as used herein is broadly defined as encompassing allstorage space in the form of computer readable mediums of any typewithin distribution storage sites.

Those having ordinary skill in the art of volume data storage techniquesmay develop other embodiments of the present invention in view of theinventive principles of the present invention described herein. Theterms and expression which have been employed in the foregoingspecification are used herein as terms of description and not oflimitations, and there is no intention in the use of such terms andexpressions of excluding equivalents of the features shown and describedor portions thereof, it being recognized that the scope of the inventionis defined and limited only by the claims which follow.

1. A composite storage server, comprising: a plurality of distributedstorage sites including a mount site, a source copy site and at leastone copy target site for executing a host job involving a storage ofvolume data within the composite storage server; wherein the mount siteis operable to communicate a source copy complete message to animmediate copy target site, the source storage complete message beingindicative of the source copy site having a complete copy of the volumedata; and wherein, based on the source copy complete message, theimmediate copy target site is operable to pull the volume data from apeer distributed storage site having a complete copy of the volume data.2. The composite storage server of claim 1, wherein the source copy siteis operable to receive a push of the volume data from a host; andwherein, subsequent to the push of the volume data to the source copysite from the host, the mount site is operable to communicate the sourcecopy complete message to the immediate copy target site.
 3. Thecomposite storage server of claim 1, wherein the peer distributedstorage site is the source copy site.
 4. The composite storage server ofclaim 1, wherein the peer distributed storage site is the mount site. 5.The composite storage server of claim 1, wherein the peer distributedstorage site is one of the other copy target sites.
 6. The compositestorage server of claim 1, wherein the immediate copy target site isfurther operable to communicate an immediate copy complete message tothe mount site, the immediate copy complete message being indicative ofthe immediate copy target site having another complete copy of thevolume data.
 7. The composite storage server of claim 6, wherein, basedon the immediate copy complete message, the mount site is furtheroperable to transition the host job from an active state to an inactivestate.
 8. The composite storage server of claim 7, wherein the mountsite is further operable to maintain the composite storage site in anormal state based on the mount site receiving the immediate copycomplete message from the immediate copy target site prior to anexpiration of a redundancy copy timer.
 9. The composite storage serverof claim 7, wherein the mount site is further operable to transition thecomposite storage server from a normal state to an immediate-deferredstate based on the mount site receiving the immediate copy completemessage from the immediate copy target site subsequent to an expirationof a redundancy copy timer.
 10. The composite storage server of claim 1,wherein each distributed storage site includes a composite storage tablefor recording host job meta-data serving as a basis for a participationby each distributed storage site in the execution of the host job. 11.In a composite storage server comprising a plurality of distributedstorage sites including a mount site, a source copy site and at leastone copy target site for executing a storage of volume data within thecomposite storage server, an immediate copy target site comprising: aprocessor; and a memory storing instructions operable with theprocessor, the instructions executed for: receiving a communication of asource copy complete message from the mount site, the source copycomplete message being indicative of the source copy site having acomplete copy of the volume data; and based on the source copy completemessage, pulling the volume data from a peer distributed storage sitehaving a complete copy of the volume data.
 12. The immediate copy targetsite of claim 11, wherein the peer distributed storage site is thesource copy site.
 13. The immediate copy target site of claim 11,wherein the peer distributed storage site is the mount site.
 14. Theimmediate copy target site of claim 11, wherein the peer distributedstorage site is one of the other copy target sites.
 15. The immediatecopy target site of claim 11, wherein the instructions are furtherexecuted for: recording host job meta-data in a composite storage table,the host job meta-data serving as a basis for a participation by theimmediate copy target site in the execution of the host job.
 16. In acomposite storage server comprising a plurality of distributed storagesites including a mount site, a source copy site and at least one copytarget site for executing a storage of volume data within the compositestorage server, a method of operating an immediate copy target sitecomprising: the immediate copy target site receiving a communication ofa source copy complete message from the mount site, the source copycomplete message being indicative of the source copy site having acomplete copy of the volume data; and based on the source copy completemessage, the immediate copy target site pulling the volume data from apeer distributed storage site having a complete copy of the volume data.17. The method of claim 16, wherein the peer distributed storage site isthe source copy site.
 18. The method of claim 16, wherein the peerdistributed storage site is the mount site.
 19. The method of claim 16,wherein the peer distributed storage site is one of the other copytarget sites.
 20. The method of claim 16, further comprising: recordinghost job meta-data in a composite storage table, the host job meta-dataserving as a basis for a participation by the immediate copy target sitein the execution of the host job.